Problem: Which of the following numbers is a factor of 72? ${2,7,10,13,14}$
Answer: By definition, a factor of a number will divide evenly into that number. We can start by dividing $72$ by each of our answer choices. $72 \div 2 = 36$ $72 \div 7 = 10\text{ R }2$ $72 \div 10 = 7\text{ R }2$ $72 \div 13 = 5\text{ R }7$ $72 \div 14 = 5\text{ R }2$ The only answer choice that divides into $72$ with no remainder is $2$ $ 36$ $2$ $72$ We can check our answer by looking at the prime factorization of both numbers. Notice that the prime factors of $2$ are contained within the prime factors of $72$ $72 = 2\times2\times2\times3\times3 2 = 2$ Therefore the only factor of $72$ out of our choices is $2$. We can say that $72$ is divisible by $2$.